Vehicle-to-grid (V2G) is a term which may be used to describe a system and or method in which plug-in electric vehicles, such as battery electric cars (BEVs) and plug-in hybrids (PHEVs) (hereinafter PHEVs), communicate with the power grid in order to be charged by the power grid or to provide power back to the power grid. V2G systems may utilize the excess battery storage capacity in the PHEVs to help stabilize the power grid. For example, V2G systems may communicate with a PHEV so that the PHEV may be recharged during off-peak hours at cheaper rates while helping to absorb excess night time electrical generation when overall demand is lower, where the vehicles serve as a distributed battery storage system to buffer power. In addition, V2G systems may communicate with PHEVs to send excess battery storage capacity in the PHEVs back to the power grid. This may help to stabilize the power grid during high-peak times and minimize potential rolling blackouts during high-peak times. A further benefit of using the electrical storage capabilities of electric vehicles is the potential mitigation to build additional generating plants to handle peak loading.
Local and federal government mandates have established guidelines for increasing the use of renewable energy sources. These mandates may have the potential to disrupt the quality of the electrical supply grid. For example, as more consumers use PHEVs to lessen the use of fossil fuels, the load on the power grid may increase as more PHEVs connect to the power grid in order to be charged. Furthermore, utilities have concerns that the increasing sale of PHEVs and clustering of PHEVs in specific geographic areas may create excessive loading to the electrical grid. Thus utilities may be interested in using electric vehicles within the V2G system framework as a possible stabilizing method for the electrical grid by providing power back to the power grid.
While there are many potential benefits to utilizing electric vehicles in a V2G system, there may be potential costs that may need to be weighed. Excessive charge and discharge cycling of an electric vehicle battery may reduce the useable life of the battery, and may lead to premature wear and warranty issues. Charging habits, or depth of discharge, may also directly affect how long the battery lasts. By avoiding fully depleting a vehicle's battery and charging frequently, the stress on a battery is reduced extending its life cycle. It would thus be desirable to provide a device and method that overcomes battery degradation in V2G systems.